Regulation of Reproductive Activity by Steroid Hormone Metabolizing Enzymes

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20a-hydroxysteroid dehydrogenase (20alpha-HSD) catabolizes progesterone, which plays a crucial role to achieve and maintain pregnancy and is a major precursor of several steroid hormones, into biologically inactive 20a-dihydroprogesterone and plays important roles in steroid metabolism. Especially in rodents, the increase of this enzyme activity in the corpus luteum causes the rapid decrease of peripheral progesterone levels and this mechanism enable rodents to actualize very short ovulation cycle (about 4 days per a cycle). Pregnancy of the rodents is achieved and maintained by the inhibition of this increase in 20alpha-HSD activity by prolactin (PRL). In this research, we studied about this enzyme and the mechanism of the regulation of the activity at cellular and molecular level, and the results are as follows.1) Ovarian 20alpha-HSDs were completely purified 2) There are two types of 20alpha-HSD with very close molecular weight (33,000) and with different ionic strengths.3) Anti-20alpha-HSD antiserum were obtained, and cellular and intracellular localization was analyzed by immunocytochemi story and western blotting.4) We found that suppressive action of PRL on the enzyme activity is mediated by transforming growth factor-beta (TGF-beta) which is produced by luteal macrophages.5) cDNA library of rat ovary was prepared to get clone of 20alpha-HSD cDNA.